CoCo 2 Memory Expansion
Scott Alfter
Yesterday I picked up a Color Computer 2 for free (somebody was
clearing house before a move). So far, I've determined that it's a
16K system with Color BASIC (as opposed to Extended Color BASIC).
Radio Shack was running a sale on CoCo joysticks ($1.99), so I picked
up one of those and some parts to hack a cassette cable together. The
only software that came with the computer was Color Scripsit in a ROM
cartridge...big deal since I normally do word processing with
AppleWorks on an Apple IIe.
Anyway...system RAM looks like it's in two 16Kx4 120ns chips. I tried
probing between the RAMs and the CPU to determine the RAM pinout, but
was unsuccessful (odds are some buffers sit between RAM and the rest
of the system). There are also two 12-pin single in-line connectors
next to the RAMs; it looks somewhat like this:
|o| |o|
|o| ___ ___ |o|
|o| -| U |- -| U |- |o|
|o| -| |- -| |- |o|
|o| -| |- -| |- |o|
|o| -| R |- -| R |- |o|
|o| -| A |- -| A |- |o|
|o| -| M |- -| M |- |o|
|o| -| |- -| |- |o|
|o| -| |- -| |- |o|
|o| -|___|- -|___|- |o|
|o| |o|
Does anybody know how to add memory to this system? I'd like to
upgrade it to 64K. I have a bank of 64Kx1 200ns chips sitting idle
that could be hacked into some sort of memory-expansion board...or
could a memory upgrade be as simple as digging up some 64Kx4 chips and
plugging them into the sockets? (That would seem plausible...16Kx4
chips are based on 64Kx1 technology, and 64Kx4 chips are based on
256Kx1 technology. I have a RAM card in my Apple that takes either
64Kx1 or 256Kx1 chips...could a memory upgrade for the CoCo really be
as simple as swapping a couple of chips?)
Before anybody asks "why are you bothering with a CoCo," let me say
that I obtained this machine to use, more or less, as a computer-toy.
I have two other systems (the aforementioned Apple IIe and a 286-12
IBM clone) that I use for real work; the CoCo is just for fun. I
started out on a CoCo back in '81...learned BASIC on it. I thought
it'd be fun to get back into it again, especially since I didn't have
to pay anything for it. :-)
_/_ Scott Alfter Internet: sknk...@cs.unlv.edu
/ v \ Call the Skunk Works BBS today! Ask me about SoftDAC--digital
(IIe ( (702) 894-9619 300-14400 V.32bis audio for your Apple IIe/IIc!
\_^_/ If Bill Clinton is the answer, it must've been a damn stupid question!!
Michael J McKenzie
>I'm not sure if this is the right place, but here goes nothing...:-)
You may find more CoCo owners through the Princeton CoCo Mailing List and
here in 'comp.os.os9'. The OS-9 newsgroup is gatewayed to a few CoCo based
networks, StGNet to name one.
>Yesterday I picked up a Color Computer 2 for free (somebody was
>clearing house before a move). So far, I've determined that it's a
>16K system with Color BASIC (as opposed to Extended Color BASIC).
(Stuff deleted.)
This sounds like the CoCo 2 version referred to as the CoCo 2B. Let's confirm
this before we go on: look at the model number underneath and see if it ends
with a 'B' as in 21-3134B. By the looks of your chip diagram it is a 2B and
so you're in luck. There are at least three ways to upgrade this computer to
64K. This model of the CoCo 2 also has real lowercase built in although you
need to do some work to access it.
The easiest method to upgrade to 64K is to find two 4464 (64Kx4 as you guessed)
DRAM chips and replace your existing 4416 chips with these. They are the same
chips that are used in IBM VGA video cards. Next, locate the
white box marked J6, jumper 6. You must solder a jumper across the two pins
in this box. Done. You now have a 64K machine.
If you want more information on the other two upgrade methods, find the
October 1986 issue of Rainbow Magazine and read the 'Turn Of The Screw Column'.
That's where I'm getting this information. The November and December '86
issues describe how to access the lowercase - requires a bit of hardware.
>Before anybody asks "why are you bothering with a CoCo," let me say
>that I obtained this machine to use, more or less, as a computer-toy.
>I have two other systems (the aforementioned Apple IIe and a 286-12
>IBM clone) that I use for real work; the CoCo is just for fun. I
>started out on a CoCo back in '81...learned BASIC on it. I thought
>it'd be fun to get back into it again, especially since I didn't have
>to pay anything for it. :-)
I hear you, I still have my CoCo 1 and 2, although I now pretty much use my
Coco 3 under OS-9. More fun than my 286 box somehow.
> _/_ Scott Alfter Internet: sknk...@cs.unlv.edu
> / v \ Call the Skunk Works BBS today! Ask me about SoftDAC--digital
>(IIe ( (702) 894-9619 300-14400 V.32bis audio for your Apple IIe/IIc!
> \_^_/ If Bill Clinton is the answer, it must've been a damn stupid question!!
Have fun!
Mike.
mjm...@unixg.ubc.ca
Scott Alfter
>In <SKNKWRKS.92...@sonny-boy.cs.unlv.edu> sknk...@sonny-boy.cs.unlv.edu (Scott Alfter) writes:
>
>>I'm not sure if this is the right place, but here goes nothing...:-)
>
>You may find more CoCo owners through the Princeton CoCo Mailing List and
>here in 'comp.os.os9'. The OS-9 newsgroup is gatewayed to a few CoCo based
>networks, StGNet to name one.
How do you subscribe to the mailing list? (I have noticed that this
newsgroup has less to do with the CoCo and more to do with the Model
100 laptop and other models.)
>This sounds like the CoCo 2 version referred to as the CoCo 2B. Let's confirm
>this before we go on: look at the model number underneath and see if it ends
>with a 'B' as in 21-3134B. By the looks of your chip diagram it is a 2B and
>so you're in luck. There are at least three ways to upgrade this computer to
>64K. This model of the CoCo 2 also has real lowercase built in although you
>need to do some work to access it.
No such luck...model # is 26-3134A. The motherboard has a different
number...20261044. As I recall, though, there were upgrade methods to
get real lowercase out of even the gray CoCos...it's not too critical,
though.
For you and all the others who've sent email regarding RAM
upgrades...thanx for the advice! I was planning on ordering some
16550 UARTs for my 286...I'll just add 4464s for the CoCo to that. :-)
Stuart Mac Glashan
Yeah, I've had a 16K Extended BASIC CoCo2 for a couple of years, and it's got
just the same sockets. I paid 28 quid for mine at Tandy, and was a little
peeved when 2 months later the 64K machine went down to the same price. Still
such is life and it's almost exactly the same as my first machine from 10 years
ago (a Dragon 32).
Anyhow, enough waffle, if there is a solution I'd be interested too.
Stuart
-( stu...@uk.ac.liverpool.compsci )----------------- Stuart Mac Glashan, -----
|\/\/\/\/\/|
| ___ ___ | "I didn't do it, nobody saw me do it,
|\|/ \/ \|/| you can't prove anything."
| \ # | # //|
| \__/ \___//||
/c \ C // |c\ "Aye Carumba !"
| c \____// |c |
\c |Re- || |c/
| |Use || ||
| |Book|| ||
------------------------------------------------------------------------------
Michael J McKenzie
>In article <mjmcken....@unixg.ubc.ca> mjm...@unixg.ubc.ca (Michael J McKenzie) writes:
>>In <SKNKWRKS.92...@sonny-boy.cs.unlv.edu> sknk...@sonny-boy.cs.unlv.edu (Scott Alfter) writes:
>>
>>>I'm not sure if this is the right place, but here goes nothing...:-)
>>
>>You may find more CoCo owners through the Princeton CoCo Mailing List and
>>here in 'comp.os.os9'. The OS-9 newsgroup is gatewayed to a few CoCo based
>>networks, StGNet to name one.
>How do you subscribe to the mailing list?
Send email to 'list...@pucc.princeton.edu' and in the body on
separate lines type 'help' and 'list'. This will send you a file of commands
explaining how to subscribe/unsubscribe to the various listserv mailing lists
along with the list of mailing lists.
>(I have noticed that this
>newsgroup has less to do with the CoCo and more to do with the Model
>100 laptop and other models.)
(Stuff deleted.)
>No such luck...model # is 26-3134A. The motherboard has a different
>number...20261044. As I recall, though, there were upgrade methods to
>get real lowercase out of even the gray CoCos...it's not too critical,
>though.
One could have true lowercase with the earlier CoCos providing you used an
external character generator that had true lowercase. The CoCo 2B uses the
6847T1 VDG (vs. the earlier 6847) which has true lowercase built in.
But you still must do a bit of hardware work to use it.
Mike.
mjmcken2unixg.ubc.ca